Regulating system



Oct. 9, 1934. GULUKSEN 1,976,613.

REGULATING SYSTEM Filed Oct. 4, 1952 2 Sheets-Sheet 2 WITNESSES: INVENTOR TTORLNEY my UNITED STA Patented a. 9, 1934 7 1,976,611 nizcum'rmc SYSTEM Finn H. Gullikscn, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of TES PATENT OFFICE I My invention relates to regulating systems, and it has particular relation to systems for maintaining constant the tension of a strand which is wound upon a reel, the effective diameter of which changes as the winding progresses.

In the case of a. reel driven by an electric motor, or other motive means, regulation of speed is required to compensate for changes in the reel diameter as the material being wound thereon 10 increases, there being a tendency for the tension of the wound material to increase as the reel fills up due to the greater peripheral speed which results from the increased effective reel .diameter. It is desirable, furthermore, to provide means for compensating for other eifects which also tend to change the tension in order to safeguard against breakage, and at the same time, to maintain high efficiency in the winding operation.

An object of my invention is to provide a tension regulating system for motor-driven winding devices which is simple in construction.

Another object of my invention is to provide a system of the type described which possesses extremely high sensitivity and regulatory precision.

A further object of my invention is to provide a tension regulating system for winding machines which are driven by direct-current-motors provided with speed control means of the electronic tube type which is reliable in operation and relatively low in cost.

An additional object of my invention is to provide a system of the type described with which anti-hunting means may readily be combined.

In practicing my invention, I provide the direct-current motor which drives the winding reel with speed-adjusting means comprising grid-controlled gas-filled electronic tubes disposed in a circuit for energizing one of the motor windings from a source of alternating-current power. The conductivity of these tubesis controlled through means preferably comprising a phase-shifting bridge circuit which impresses upon the tube grid elements a control voltage.

-'I'his bridge circuit contains an adjustable element which is influenced by a member the position of which is determined by the tension of the strand being wound upon the reel. In this manner, a change from the desired value of the strand tension is caused to efi'ect an appropriate corrective change in the speed of the driving motor, which tendsto restore the strand tension to the desired value.

My invention will best be understood from the following description of specific embodiments thereof, when taken in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of apparatus and circuits illustrating an embodiment of my 00 invention in which the tension-responsive member varies the illumination on a photo-cell that is disposed to influence the phase-shifting bridge circuit of the speed-adjusting means for the reel driving motor.

Fig. 2 is a diagram of vectors illustrating the action of the phase-shifting bridge circuit utilized in the system shown in Fig. 1. V

Fig. 3 is a diagram showing the manner in which the electronic tubes utilized by the system 79 shown in Fig. 1 function to rectify and control the magnitude of the energizing current supplied from an alternating-current source of power to the field winding of the reel-driving motor, and

Fig. 4 is a diagrammatic view of apparatus and circuits arranged in accordance with a second embodiment of my invention in which the tensionresponsive element directly acts to mechanically adjust a rheostat disposed in the phase-shifting bridge circuit. 80

Referring to the drawings, and particularly to Fig. 1 thereof, the reel upon which the strand or web 10 of material whose tension is to be regulated is being wound is shown at 12. Reel 12 is driven by a direct-current motor 14 which comprises an armature winding 15 which may be energized from some suitable source of direct-current potential represented by circuit conductors 16, and a field winding 18 which is shown as being energized by direct-current from rectifying 99 means comprising electronic tubes 20 and 22, which tubes are supplied from a source of alternating current potential, designated by conductors 24 and 25, through a transformer 2'7.

'The tension on the strand 10, being wound upon the motor driven reel 12, may be changed by adjusting the speed of driving motor 14. This change is effected, in the system shown in Fig. 1, by means of a target or counterweight 85 arranged to vary the strength of a beam of light to 100 increase the illumination on a photocell 64 when the length of the strand loop which supports the counterweight 85 increases. The increase in illumination results in a decrease in plate current of an amplifier tube 62 which, acting through a 9 phase-shifting bridge circuit 48, serves to lower the efiective conductivity of a pair of electron tubes20 and 22 that are connected in the energizing circuit of the motor field winding 18. The decreased motor excitation causes the motor to By the application of the photocell and an intercepted light beam, the control apparatus employed possesses the advantage of not being subject to wear and of being highly accurate and sen,- sitive. means, represented as employing a series connected resistor and a condenser that are energized by the voltage appearing across the motor field winding 18, may be utilized.

The electronic tubes 20 and 22 are preferably of the well-known grid-controlled gas-filled type. As shown, tube 20, for example, comprises two major elements, an anode or plate 29, and an electrically heated cathode 30, and one minor or control-grid element 32. Tube 22 will be seen to similarly comprise anode, cathode and grid elements 34, 35 and 36, respectively.

When disposed in the manner shown tubes 20 and 22 effect full-wave rectification of the alternating-current that energizes the motor field winding 18, it being observed that the tubes are disposed in circuits that include as an energizing source the portions of the secondary winding 38 of transformer 27 on opposite sides, respectively, of a mid-tap connection 40.

The tubes possess the well-known characteristic of passing current between the major elements in one direction only, from anode to cathode, so that, when energized from an alternatingcurrent source, current passage can take place only during the positive half cycle of the tube anode voltage. Thus, when connected as in the system of Fig. 1, tube 20 passes current through motor field winding 18 during the half of the alternati'n'g current cycle in which the upper end of transformer winding 38 is positive with respect to the lower portions thereof, while tube 22 similarly passes current during the other half-cycle in which the lower end of winding 38 is at a posi-, tive potential with respect to the upper portions thereof. It will be observed that this winding energizing circuit is completed through a conductor 42 joined with the mid-tap connection of a cathode heating transformer 44 and a second conductor 45 that connects winding 18 with the mid-tap of transformer 27.

In a tube of the type under consideration the portion of this positive half cycle during which conduction takes place and hence the eifective current passed may be regulated by suitably modifying the control potential impressed upon the grid element of the tube. Thus, in order that the tube conduct current through its major element circuit, it is necessary that the control grid element be maintained at a potential in excess of some givencritical value. Such a series of minimum or critical values of grid voltage is represented in Fig. 3 by curve EX, which curve is related to the wave. of anode voltage Ep impressed upon the major element circuit of the tube in the manner shown.

Curve Ex will be recognized as applying to a In a system of this type anti-hunting.

tube behaves in a manner that if a negative bias bemaintained on the grid in excess of a given series of values throughout the cycle no current conduction between the major elements can take place. However, if this negative grid bias voltage falls below the critical value indicated by Ex, conduction from that point during the remainder of the positive half cycle will take place. Consequently, when the position of a wave of grid voltage -is that represented by curve E; in Fig. 3, current conduction will result during the shaded portion of the positive half cycle. As will be, apparent, the starting point of such conduction may be changed by shifting the point of intersection of the control potential curve Eg with the critical voltage curve Ex.

To eifect a control of the position of the grid voltage wave E; with respect to the anode voltage wave E the phase-shifting bridge circuit 48 is disposed intermediate the source of grid voltage and the control elements of the tubes. Bridge circuit 48 is shown as being energized from alternating-current source conductors 24 and 25 through a transformer 50, having a secondary winding 51 which serves to energize a capacitor 53 in series with a full-wave rectifier 54. The common point 55 of the two elements just named is joined with one end of the primary winding of a grid coupling transformer 57, the other end of the primary winding of which is joined with a mid-tap connection 58 oftransformer winding 51.

The direct-current terminals of the .rectifier 54 are connected to the plate and filament elements 60 and 61 of a vacuum tube 62, the im-. pedance of which tube is controlled by the magnitude of the potential impressed upon the grid element 63 thereof through a circuit which includes, as a controlling element, the photo-cell device 64. Thus, the rectifier 54 and tube 62 together, act as an adjustable resistance, adjustment thereof being eifected by changing the grid potential of the tube.

The alternating-current voltage from the transformer 50, acting upon the rectifier 54 and the capacitor 53 in series,- produces in these elements potential drops Er and Ec, respectively, having some such phase relation as is indicated in Fig. 2. In this figure vectors E1 and E2 indicate the voltages acting in the two halves of transformer winding 51, while vector Eg designates the potential acting between points 55 and 58 of the bridge circuit, which potential is impressed upon the grid elements of the electronic tubes 20 and 22 by means of the coupling transformer 5'7. For a given value of grid bias on vacuum tube 62 the control voltage thus impressed upon the grid elements of tubes 20 and 22 may be displaced by angle 0 from the main power voltage Ep acting between circuit conductors 24 and 25 which voltage is, as has been mentioned, impressed through transformer 27 upon the major elements of tubes 20 and 22.

Photo-sensitive device 64 may be of any suitable type capable of changing its resistance in accordance with the intensity of illumination. As shown, it comprises an anode and a cathode element 66 and 6'7, respectively, enclosed in a gastight chamber 68. Element 67 is coated with an electron emissive material which becomes active when light falls thereon. Consequently, in the absence of illumination, device 64 is incapable of conducting current when placed in a dihot cathode tube of the mercury filled type, which mot-current circuit, while when it is illuminated it takes on the property 01' a resistor, the effective resistance or which varies inversely with the 11- lumination intensity.

The device 64 is connected to control the-magnitude of a direct-current potential applied to a grid element 63 or vacuum tube 62 through a circuit which includes a resistor arranged to be energized by a direct-current potential derived i'rom any suitable source, such as from alternating-current conductors 24 and 25 through a full-wave rectifier 72 and filtering apparatus '13. To adjust the magnitude of the voltage impressed upon resistor 70 a potentiometer comprising resistor 74 and an adjustable tap connection 75 may be provided.

The photo-cell 64 will thus be seen to be in a circuit supplied by the voltage acting across the resistor 70 which circuit includes a resistor 77 connected in series with the cell. The cathode element 61 01' the vacuum tube 62 is connected by means of a tap connection 78 with an intermediate point of the resistor 70, while grid element 63 of the tube is connected through a circult which includes resistors 79 and 80 with the point 81 of photo-cell energizing circuit.

To control the intensity of illumination of the photo-cell 64 in accordance with the tension of strand 10 being wound upon the reel 12, I provide a member 85, supported at the upper end by a pulley 86, which rides in a loop in the strand. Preferably, a tension spring 87 ass sts the weight of the member in opposing the upwardly acting force exerted thereon by the tension of the strand. When this tension is of the desired value, the member 85 will occupy some intermediate position, such as shown, a decrease below the desired value of tension allowing it to move downwardly, and an increase above the desired value causing it to move upwardly.

Such movements control the intensity of light that falls upon the photo-cell 64 from a light source, such as a lamp 88, through a lens 89. As the member rises, the illumination of the photocell will be decreased, while as the member moves to a lower position it will act to increase the illumination.

To place in operation the system of my invention shown in Fig. 1, the control switch 1'7 is first closed to complete energizing circuits for the windings of motor 14. The winding reel 12 thus being rotated, when the 'material being wound thereon is of the desired tension, photocell 64 will be illuminated at some intermediate intensity, which causes a voltage of intermediate magnitude to be impressed upon the grid element 63 of the vacuum tube 62. This acts upon the phase-shifting bridge circuit 48 in a manner to give to electron tubes 20 and 22 an intermediate value of effective conduction, which conduction is suilicient to maintain the excitation of the reel driving motor 14 at the value necessary for the proper speed thereof.

A decrease below the desired tension of the strand 10 serves to increase the illumination intensity of photo-cell 64 which increases the conductivity of the cell. This increases the current through series-connected resistor 77 and by increasing the voltage drop through the resistor makes the grid bias of the vacuum tube 62 more negative with respect to the filament 61 of the tube. The consequent decrease in tube conductivity increases the eiiective resistance of the rectifier 54 in the phase-shifting bridging circuit 48, causing the voltage drop Er across the rectifier to increase and the voltage drop Ec across series-connected condenser to decrease. As will be seen by an examination of Fig. 2, this efiects an increase in the displacement angle theta oi the control voltage E; applied to the grid elements of electron tubes 20 and 22.

Such increase in displacement, as an examination of Fig. 3 will reveal, shifts the current conduction starting point of the tubes to a latter point in the positive half-cycle of anode voltage. The resulting reduction in efiective energizing current supplied through the tubes to the field winding l8 of reel-driving motor 14 causes the motor to increase its speed thereby raising the tension of strand 10 back to the desired value.

It will be apparent that an increase in strand tension decreases the illumination intensity of photocell 64, and thus institutes a series of eiiects exactly opposite to those just described for an increased photocell illumination, the final result being to increase the field winding current and to reduce the speed of the winding reel 12, which effects the necessary reduction in strand tension. In order to prevent overshooting of the corrective action which, in a highly sensitive regulating system of the type just described, would other- 100 wise be likely to occur, I provide anti-hunting means, previously mentioned as comprising the resistor 80 and thecondenser 90 connected in series across the motor-field winding 18. As shown, these two elements derive their energization through a filter circuit 92, which is associated with an anti-hunting-sensitivity-adjusting potentiometer comprising resistor 91 having a tap connection 93. The purpose of the filter apparatus is to prevent the current pulsations which 110 act upon the motor field winding 18 from reaching the anti-hunting elements, 60 and 90. The anti-hunting circuit shown in Fig. 1 is the same as that disclosed .and claimed in a copending application of J. H. Ashbaugh and myself, Serial 1 5 No. 543,514, filed November 11, 1931 and assigned to the same assignee as this invention. As is explained in that application, such antihunting means serves to stabilize and prevent overshooting of the corrective action by modifying the corrective changes in the electronic tube grid bias in accordance with the direction and rate of change of the motor field winding current, the efi'ect being to retard the corrective action as the desired value of regulated quantity is approached.

Thus in the system of Fig. 1, adjustment of the excitation of the reel-driving motor 14 in the strand-tension-raising direction, or, in other words, a decrease in the energizing current of, and 3 the voltage appearing across the field winding 18, allows the condenser 90 to send a discharge current through the resistor 80, which forms a part of the grid element energizing circuit ofvacuum tube 62. The polarity of the voltage drop in the resistor 80 is such as to make the grid bias oi the tube 62 more positive with respect to the filament and to thus prematurely arrest the corrective action which was instituted by photocell 64. Similarly, a corrective action in the opposite direction, by raising the voltage across the motor field winding 18 causes the condenser 90 to draw a changing current which, flowing through the resistor 80, sets up in the resistor a voltage drop in the opposite direction, which drop serves to arrest the corrective action instituted by photocell 64 and prevents overshooting thereof.

Thus it will be seen that the effect of the antihunting means just described is to modify regulain accordance with the direction and rate or change in the energizing current in the motor field winding 18, the effect being w arrest the regulatory change as the desired tension 0! the strand is approached.

For situations in which extremely accurate regulation is not required, the system shown and described in Fig. 1 may be simplified in the manner indicated in Fig. 4. It will be observed that the rectifier unit 54 in the phaseeshitting bridge circuit 48 of Fig. 1 has, in the system shown in Fig. 4, been replaced by rheostat 96, which rheostat is disposed for direct mechanical operation by the movement of tension-responsive member 85. As will be observed, the vector diagram or Fig. 2 applies to the modified phase-shitting bridge circuit 48 of Fig. 4.

- In operation of the system 01 Fig. 4, a decrease in the tension 01' strand 10 allows slider member 98 to move downwardly along the resistor thereby increasing the resistance of rheostat 96. By thus increasing the voltage drop Er and lowering the voltage E; the displacement angle theta of the control voltage E. impressed upon electron tubes 20 and 22 is increased and the conductivity of the tubes is correspondingly lowered. The resulting decrease in energizing current supplied to motor field winding 18 causes the motor to speed up and thereby raise the tension of strand 10.

It will be apparent that an increase above the desired. value in strand tension lowers the resistance of rheostat 96 and thereby causes the conductivity of tubes 20 and 22 to be increased, which in turn, increases the motor excitation which lowers the motor speed. This reduction in speed serves to lower the strand tension back to the desired value;

The critical voltage drop Ex of Fig. 3 applies, as has been mentioned, to a grid-controlled tube of the hot cathode mercury filled type. As pointed out, other equivalent types of tubes may also be successfully used in the systems oi! my invention. For example, grid controlled tubes of the hot cathode neon gas filled type, the mercury pool type, as well as of the cold cathode type as are well known. The critical voltage characteristics of this last named type of tube differ somewhat from those given by curve Ex of Fig. 3. However, the eiiect of shifting the phase position of grid potential curve E; with respect to the main power voltage curve E]: is exactly comparable in those situations as in the one explained although the exact values of displacement would, of course, be somewhat modified from those which applied to the mercury tube characteristic illustrated. It will be noted, therefore, that the system of my invention may utilize grid-controlled tubes of a wide variety or types.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In a system for regulating the tension of a strand being wound upon a reel, the combination with a motor for driving said reel, of means, comprising a grid-controlled gas-filled electron-discharge tube, for controlling the speed of said motor, a phase-shifting bridge circuit, having an adjustable resistance element, for impressing a control potential upon said tube, a member whose position is determined by the tension of the strand being wound on the reel, and means comprising a the intensity of said illumination.

photo-sensitive device and a light source therefor, ior varying the resistance oi said adjustable element in the bridge circuit in accordance with. the position of said tension-responsive member.

2. In a system for regulating the tension or a strand being wound upon a reel, the combination with a motor for driving said reel, of means, comprising a grid-controlled gas-filled electron-discharge tube, ;or controlling the speed 0! said motor, a phase-shifting bridge circuit, for impressing a control potential upon said tube, a rectifier disposed in said circuit, a vacuum tube connected with said rectifier, a photo-sensitive device disposed to influence said vacuum tube, means for illuminating said photo-device, and means responsive to the tension of the strand being wound on the reel for determining the intensity of said illumination. s

3. 'A system for regulating the tension of a strand being wound upon a reel comprising in combination, a direct-current motor having field and armature windings for driving said reel, a grid-controlled gas-filled electron-discharge device disposed intermediate a source of alternatingcurrent power and one of said motor windings for the purpose of controlling the energizing current supplied thereto, a bridge-circuit for impressing a control potential upon said device, an adjustable element disposed in said circuit for shifting the phase position of said control potential, a photosensitive device disposed to influence said adjustable element, means for illuminating said photodevice, and means responsive to the tension of the strand being wound on the reel for determining 4. A system for regulating the tension of a strand being wound upon a reel comprising in combination, a direct-current motor, having field and armature windings, for driving said reel, a grid-controlled gas-filled electron-discharge device disposed intermediate a source of alternatingcurrent power and one of said motor windings for the purpose of controlling the energizing current supplied thereto, a bridge-circuit for impressing a control potential upon said device, an adjustable element disposed in said circuit for shifting the phase position of said control potential, a photo-sensitive device disposed to influence said adjustable element, means for illuminating said photo-device, and means responsive'to the ten-' sion of the strand'being wound on the reel for determining the intensity of said illumination, said means comprising a light-intercepting shutter the position of which varies with the strand tension.

5. In a system for regulating the tension of a strand being wound upon a reel, the combination of a motor for driving said reel, electronic-tube means for regulating the speed of said motor, a circuit for controlling said electronic-tube means, 135 a photo-cell connected in said circuit, a source of, light for illuminating said cell, a shutter disposed intermediate the light source and the cell, and means for causing the tension of the strand being wound on said reel to determine the position'of 140 said shutter.

- 6. In combination, a direct-current motor having field and armature windings, a grid-controlled gas-filled device, disposed intermediate a source of alternating current power and one of said 145 motor windings for the purpose of controlling the energizing current supplied thereto, a bridgecircuit, having an adjustable phase-shifting element disposed'therein, for impressing a control potential upon said device, a photo-cell disposed 5 trol the speed of the motor by varying the energization of said winding, means responsive to the tension of said strand for influencing said speedadjusting means, and means acted upon by the voltage appearing across said motor winding for modifying the tension-responsive influences upon said speed-adjusting means in a manner to prevent over-shooting of the regulatory action.

FINN H. GULLIKSEN. 

